June flood ‘not extraordinary,’ expert research shows

Colette Derworiz, Calgary Herald11.29.2013

The devastating June flood in Calgary was not a one-in-100-year event as the province’s analysis suggests, but a one-in-45-year event, according to University of Saskatchewan research that examined patterns as far back as the late 1800s, raising a warning of the need for a better flood plan.

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CANMORE — The June flood was not the deluge of the century and could happen again in our lifetime, says the Canada research chair in water resource and climate change.

During a talk in Canmore this week, hydrologist John Pomeroy said he and his University of Saskatchewan colleagues went back further than available data from the Water of Survey of Canada and studied floods dating back to the late 1800s and early 1900s through older Geological Survey of Canada records.

“The flood of 2013 was big and, for many people, utterly devastating, but it was not extraordinary,” he told those gathered for the presentation. “It was not the flood of the century and, unfortunately, probably not even the flood of a lifetime.”

Pomeroy said the statistical review shows it was a one-in-32-year flood in the Banff area, and a one-in-45-year flood in Calgary.

“We have to expect events like this again and we have to look at how we are going to mitigate against events like this,” said Pomeroy, suggesting that means better forecasting and warning systems, a ban on development in flood plains and active mitigation with berms and dams.Officials with Alberta Environment and Sustainable Resource Development said the province’s current analysis of data still suggests it was a 1-in-100-year flood.

“That is what the models are based on,” said spokeswoman Nikki Booth.

However, she said they welcome any new information as department staff plan for the future.

“They will definitely be looking at the same data that Dr. Pomeroy has looked at,” she said. “We’re not ruling anything out.

“We want as much information as we can get.”

The information should also be noted by municipalities such as Canmore and Calgary, according to water expert Robert Sandford.

“We had a really heroic effort in responding to the floods,” said the Canadian chairman of the UN Water for Life Decade initiative. “We should have equally heroic efforts in protecting the city from future floods.”

Calgary, he suggested, is currently the most vulnerable city in the country when it comes to flooding.

Mayor Naheed Nenshi was not made available for comment Wednesday or Thursday, but Canmore mayor John Borrowman said the data echoes what they’ve heard from the independent consultants hired by the town: that it was a one-in-30-year event in the Banff area.

“It’s a little daunting to see it,” he said.

However, Borrowman said he’s confident the town will be able to protect itself from future flooding with the mitigations they’ve approved — particularly for Cougar Creek, which caused the worst damage in the June flooding.

The town has approved $14 million to put in a debris net upstream to capture sediment before it arrives in the creek and reduce erosion to prevent property damage. There’s also some work being done in the creek’s channel.

Pomeroy said the latest information makes it clear municipalities and the province have to do things differently.

“The middle and later part of the 20th century was an exceptionally moderate period without really any substantial flooding since 1932 in the area,” he said. “That, I think has lulled us all into the belief that we could live in flood plains, that we don’t need to build our bridges very high, that we could manage our dams in a pretty relaxed manner.

“What we’ve seen is an event more like the early 20th century, late 19th century, which suggests those are completely inadequate.”

Pomeroy said, however, there are major differences in the June flood compared with the historic floods.

“Winters are about five degrees warmer now than they were in the late 1800s,” he said. “We don’t have vast glaciers in the Bow Valley draining in cold, wet systems in there, we have droughts as well. So we’re actually modulating between floods as severe as in the end of the little Ice Age along with droughts in the last 10 years that are worse since settlement.

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